1. Field of the Invention
The present invention relates to a lapping monitor element that is juxtaposed with a magnetic transducer element having a magnetoresistance effect film in order to determine the lapping position of a substrate, upon lapping the element height of the magnetic transducer element to a desired dimension. The invention relates further to a combination consisting of the magnetic transducer element and the lapping monitor element, and to a method for manufacturing the magnetic transducer element.
2. Description of the Related Arts
With a growing tendency toward miniaturization with large capacity and toward higher recording density, a magnetic disk drive is being required to improve the performance of its thin film magnetic head. To this end, a composite thin film magnetic head is widely used as the thin film magnetic head, in place of a thin film head effecting record and reproduction through an induction type electromagnetic transducer element. The composite thin film magnetic head is of a structure where a recording head with an induction type magnetic transducer element for write is laid on a reproducing head with a magnetoresistance effect element (hereinafter referred to simply as MR element) for read.
As used herein, the MR element refers not only to elements using magnetoresistance effect materials represented by NiFe but also broadly to elements using multilayered materials indicative of magnetoresistance effect, such as a spin valve, TMR (ferromagnetic tunnel effect) and CPP(Current Perpendicular to the Plane)-GMR (Giant Magneto-Resistance).
Up until now, the manufacture of the composite thin film magnetic head includes a polishing (lapping) step of adjusting the element height of the MR element (hereinafter referred to simply as MR height) to a predetermined level. Traditionally, to adjust the MR height to a predetermined dimension, a specific technique is employed, where an ELG (Electric Lapping Guide)sensor acting as a lapping monitor element is separately placed next to the proper MR element. Thus, while measuring the values of resistance of the ELG sensor caused by the lapping device and converting the measured values to the height of the MR elements, the lapping step of polishing up to the MR height is carried out.
Besides the ELG sensor, the lapping monitor element is also known as RLG (Resistance Lapping Guide) sensor, but their basic actions are the same and in this specification for convenience they are unified under the term ELG sensor.
Referring to FIGS. 19A and 19B there is shown an example of the conventional techniques, where the ELG sensor and the magnetic head having the MR element are disposed side by side. FIG. 19A is a sectional view of the layered state, and FIG. 19B is a top plan view of the same.
In FIGS. 19A and 19B, lower shields 102 are isolatedly separated from each other by way of separation layers 103 of Al2O3 etc., over which a nonmagnetic gap film 105 is formed. On top of the gap film 105, an MR element 100 including a magnetoresistance effect film (hereinafter referred to as MR film) 120 and an ELG sensor 200 including a lapping monitor film 220 are arranged side by side. A pair of leads 110 and a pair of leads 210 are attached respectively to both ends of the MR film 120 and both ends of the lapping monitor film 220. Then, the whole plane, indicated by a lower line li in FIG. 19B, is lapped so that the direction of the arrow (α) becomes shorter and when the predetermined MR height is reached, the lapping comes to a stop (for example, if line lf is the level at which the lapping should come to a stop, the length H in the diagram is the MR height).
Typically, the resistance of the lapping monitor film 220 of the ELG sensor 200 is measured and converted into the MR height using for example design values of the ELG sensor, and thus it is determined whether the predetermined MR height has been reached or not.
Typically, the lapping monitor film, which is a resistor used in the ELG sensor, lies in the same layer together with the MR element, as disclosed in Japanese Patent Laid-open Pub. No. 2000-6129 for example, with a view to reduction in the number of steps or simplicity of the manufacturing process. More specifically, in case of the example of FIGS. 19A and 19B, the MR film 120 and the lapping monitor film 220 are composed of a multilayered film of completely identical material, so that the lapping monitor film 220 can also function as the magnetoresistance effect film.
During the lapping step, however, a magnetic field may appear irregularly from the lapping device and adversely affect the determination of the MR height (this problem was presented for the first time by the present inventors). More specifically, since the ELG sensor uses the same layer together with the MR element, it may occur a magnetoresistance change due to the irregular magnetic field from the lapping device upon lapping, which resistance change may cause a change in the measured values of the ELG sensor. For this reason, the resultant MR height may become uneven, making it difficult to provide a precise MR height control upon lapping. This problem will become more remarkable accordingly as the rate of change in the resistance effect of the magnetoresistance effect film used in the MR element rise as a result of technical progress.
In other words, a higher recording density causes a greater demand for the improvement of output of the reproducing head, whereupon the rate of change in the resistance effect of the magnetoresistance effect film used in the MR element is steadily improved and increased to a large extent. Thus, with increased rate of change and raised sensitivity, the above problem that occurs during the lapping step will become even more remarkable.